You can buy a simple but useful ready-made 2.4" TFT oscilloscope on eBay for about £10. Putting one behind a Kosmo panel should be quite easy.
Look for the model number DSO138.
See also this post I made showing my own DSO138 in its case, which costs another £5 or so but probably wouldn’t be needed in a Kosmo module.
Dso 150 is good for kosmo as it fits behind a 10x20cm panel and you dremel a square out for the screen, can add a mixer as the input.
https://www.thingiverse.com/thing:3631288 This is how to convert it to eurorack (same as dso138).
Here is my take, pretty scuffed but works kinda.
Nice.
At $0.73 shipped (!!!) it’s hard to argue against that power board but does it actually do anything in this context an L7805 wouldn’t? [Edit: 7809, I meant] You don’t need to boost and you don’t need the adjustment.
I have a DS202 handheld scope which is okay, if a bit fiddly to operate, but my main gripe with it is that I have trouble getting it to trigger on sub-audio frequency stuff. Down to around maybe 60 Hz it’s okay but lower frequency or sporadic things it seems very hit or miss whether it’ll trigger. Perhaps it’s pilot error but I’ve used scopes for 40 years and it seems like I should be able to figure it out. Does the DSO 150 trigger on low frequencies reliably?
It doesn’t trigger very well on low frequencies no, sometimes it does but it does the job anyway, and I just followed what the other guy did I linked, any voltage regulator would do.
Now I see in the comments one user asked about the regulator:
I think the scope is speced for 8-12V supply…? It feels weird to me to go via 5V rail and boost converter? For me this would be coming from a lm7805 from the +12V rail. And then using a boost converter from 5V to 9V and then it’s actually converting this back to ±5V on the scope with lm78l05/lm78l09
I’m thinking maybe I’ll just go with +12V and put two small heatsinks on the regulators if they get too hot?
and ended up just connecting the scope to the 12V bus:
Yes, went straight from positive rail on my eurorack. Seems to work fine, but I don’t have many hours of runtime so at your own risk
But I’m pretty sure the regulators on the board have overheat protection so it will shut down if it gets too hot. I didn’t even bother with a heatsink. Input voltage is rated 8-12V on the DSO138 so should be fine.
fwiw, JYE says:
DSO Shell runs on 9V (do not use power voltage higher than 10V!) power supply.
and “Supply Current: 120mA @ 9V” so a 7809 on the +12V sounds like a reasonable supply, if you prefer to stay within spec ((12−9)×0.120=0.36 W ×~60 °C/W to air so shouldn’t get too hot).
Right, the original DSO138 is “9V DC (8 - 12V acceptable)”, the DSO138 mini is “3.5V - 6V DC”, and the Shell (DSO150) is as you say “9V DC (8 - 10V acceptable)”. It pays to read the fine print!
The 5v rail infact couldn’t seem to power the oscilloscope at 9v, highest the voltage converter would go is 7v before it failed, still works fine though, I changed my input current from 1A to 3A that would probably allow 9v though I will leave it as it is. Don’t know if it would have been better to step down the voltage from the 12v rail.
I run my stand-alone DSO138 scope from a 12v DC supply because that’s what I found in my spares box on the day I tested it. 12V DC is within the recommended supply range for the board so I don’t see why you’d need to muck around with the 5V Eurorack rail, which is usually rather anaemic if supplied at all.
I do get that this class of scope is not universal, and there are many things it will never do at all well (RF and LFO for instance.) It’s pretty good at taking “Polaroid”-like snapshots of audio signals within the typical modular range, though.
I thought the DSO150 must be an advanced version, maybe with a bigger screen, but on eBay the items I see seem to be pretty similar to the DSO138, with the exception that their operating power range has a 10V ceiling. Inconvenient for Eurorack power supplies.
Is there an obvious technical reason to favour DSO150 over DSO138, given the identical 2.4" screens?
Added later: there are available firmware upgrades for DSO138 to add a second channel. Some soldering may be required to get the most out of it.
From the link Fredrik gave above:
DSO Shell (DSO150) Oscilloscope has similar bandwidth as DSO138 but contains significant improvements in structure, mechanical, and operation.
- Display and MCU are now mounted on the same board (mainboard) to avoid using inter-board pin-headers
- Main board can be used as a flexible general purpose controller
- Comes with full enclosure. The front panel and top/bottom brackets are flexable for easy user modifications
- Rotary encoder has been added which makes parameter adjustment much quicker and easier
- Sensitivity has been extended in both directions and is higher and wider than DSO138, reaching 5mV/div — 20V/div
It’s good value for money, if you want a case or have a use for the extended range. If I were to integrate a device like this into a rack modular, though, I might want to switch out all of the front panel gear for something that would harmonise with the general design of the synth, and the item wouldn’t need a case. In that event I wouldn’t be that impressed by the difference.
Then again, I don’t see much point in pinning an oscilloscope down on a rack, except perhaps to enhance the coolness factor of the rack. So it’s a largely academic point for me, which is better. I can’t see a good use case for integrating a scope into a rack.
On the topic of oscilloscope modules, somebody is selling an inexpensive DIY conversion kit for the DSO150, called Euroscope Mk 2. There is also some advice about which is the best version of DSO150 to get (the original 2017 version which they say is available from Banggood.)
that is freaking awesome!
Yeah I’m tempted to design a faceplate just for the cool factor. Even with the screen and buttons and adding in and out jack you would have some space for something else…hmmm
I want a PCB and Panel for the Gameboy Triple OSC… lol
I know its probably a pain in the assss but I waaaant!
that is definitely on the to do list! I’m sorry its taken so long!!! I have a lot of them on the go at the minute. rest assured it will be one of the next wave!! got a mega drone module and 6 channel midi to cv on the way next. then faffing on a delay and a noise crescendo module then lets see!
Midi to cv would be a miracle for me.
I agree with @Caustic! I’m in dire need of a midi to cv module. Right now I don’t have a way to use any of the other modules I have. With everything going on is there a way that you could supply a parts list for the midi to cv and VCA so that we could try and get the parts ASAP? Mouser is still shipping right now, but they may not be a week from now. If I’m going to be stuck in my house for 3 more months I’d love to be able to use these awesome modules you’ve created! 
You could do a midi to cv module with an Arduino, an optocoupler and a DAC pretty easily, so if you wanted to source the parts, I’d start with Everything in the last section of this instructible Then add a DAC (I like the Adafruit MCP4725 breakout, but they shut down their operation for the time being so unless you can find one aftermarket on eBay or something you may be out of luck.)
